1. Field of the Invention
The present invention concerns a self-stripping connection device allowing for the rapid establishment of a contact between the conductors of insulated wires and an electrical terminal (intermediate connecting piece) without preparation of the insulated wires.
2. Description of the Prior Art
Generally, to establish an electrical connection between a terminal and a wire, several tools must be used, each of which allows the cutting, stripping and connection of the wire to the connector. In addition to the time and the skill necessary for such separate operations, the risks are great that there will be an intermittent failure or incomplete connection as a result of these separate processes. Indeed, when the core of the conductor is excessively cut by stripping or is excessively stressed by crimping, eventual rupture of the wires becomes a risk.
More recently, self-stripping contact devices have been utilized, which cut the insulating cover of the wires and strip the metallic conductor to establish a contact. Although this type of connection has the advantage of simplicity and speed, it requires the use of a specialized tool. Indeed, some tools require another special tool, in order to introduce the wires into the connecting device.
Moreover, contact devices are generally critical in regard to their support and their ability to withstand separation of the wires. The prior art devices, by damaging the wires, provide insufficient support and are also very sensitive to the phenomenon of corrosion.
Many diverse types of self-stripping connectors are known, for instance those which are described in European Pat. No. 0 002 113, West German Pat. No. 3 150 951, and French Pat. Nos. 2 251 927 and 2 561 825.
However, it seems clear that the principal difficulty with the prior art is the engagement of the wire into the engaging slot. In order to introduce a conductor into a slot of small size, it is necessary to apply a considerable symmetrical force on the wire on all sides of the wire as it is pushed into the slot. Otherwise, the connector will bend or break and it will not be possible to connect to it.
In the case of contact with circular slots, lateral force is also required because the wire is perpendicularly inserted and it is difficult to grasp the wire.
In European Pat. No. 0 002 113, the transmission of the movement to create the connection is made through the device, but that technique, if it is to work, employs a complicated and large mechanism and is thus costly.
In W. German No. 3 150 951 and French No. 2 251 927, the problem is resolved by using a tool which forms the two lips of the engaging, circular slot from two moveable pieces which rotate in opposition to each other. The connecting wire is introduced into the two opposing pieces and by rotation of one or the other, the connection is established. This technique has a number of drawbacks. In addition to it having two moveable parts that are not utilized in the contact, the stripping of the wire is only effected on the lip of the moveable slot, wherever the wire happens to be. The stripping of the wire is not accomplished in a symmetrical fashion at the core of the conductor, and thus there is a considerable risk that the insulation will "creep" over the connection, making good electrical contact impossible.
In FR No. 2 561 825, the self-stripping contact is without a slot, which simply permits the contact to take the shape of the barrel in order to be able to carry along the wire on either side of the point of contact. The corrective technique of providing a slot, though appearing obvious, has a major weakness because the pressure on the contact is caused by the plastic skirt of the barrel. One might think that the pressure of the contact exercised by this skirt is sufficient. It is however not likely that the insulation of the wire, which serves as an intermediary, could provide support under prolonged pressure without "creeping".
Besides the drawbacks noted above, the size and weight of these connectors are of the order of 10 times the diameter of the wire that needs to be connected. These dimensions prohibit the use of such contacts in average applications particularly when the required size of connectors is further decreasing.